What is a Go-Kit? A Go-Kit is a portable amateur radio
station
which the radio amateur can take when asked to go to an event which
needs support with radio communication. What is consists of
depends on the extent of the event, and the communication needs. Making
a pre-planned kit helps the thought process as to what will be needed,
and how it will be used. What I present here is the thought process
which resulted in my current Go-Kit, which might inspire you to improve
on it.

Recently, we had a triathlon in our town, with 600 entrants.
The
ham radio community was asked to help with communications, and many
volunteers showed up to assist. Communications for the event
were
handled through two of our closest repeaters which were linked together
for the event to provide nearly seamless communication throughout the
community. Some of the volunteers showed up with a 2 meter
HT,
and nothing else in the way of communication equipment. Even
with
the best of repeater support, there were times when communications were
spotty because of the low power hand-held transceivers, and the hilly
terrain. I have seen this problem many times before, and it leads me to
my first point. Sometimes it is necessary to go equipped with
more than QRP (low power) equipment to achieve reliable
communications. It is good practice to use no more
transmitter
power than required, but it is also necessary to have enough power
available to complete the communications. This has led me to
build a Go-Kit which is capable of more transmitter power than my
HT. I do not have to use that power, but if I need it, it is
there.

Sometimes also it is useful to have more than VHF/UHF
capability.
Depending on the event, it may or may not be possible to rely on
repeaters to extend the range of hand-held, mobile, and portable
stations. In major emergencies, it may not be possible to rely on the
presence or operation of repeaters, and so longer range communications
must be established some other way. This may be by
well-situated
stations, or stations with higher power and/or better
antennas.

My first Go-Kit was based on a Yaesu FT-817 Ultra-Compact QRP
radio. This is a particularly fine choice as it is very
compact
and portable, completely self-contained radio which covers most every
ham band between 1.8 and 450 MHz, on FM, SSB, CW, and digital
modes. I combined this with an LDG Z-11 tuner, and a W4RT
Electronics One-Touch-Tune module. This served me well, with
the
exception that sometimes the five watts that the FT-817 produced was
just not enough to reliably get through, due to terrain, propagation,
and other issues.

Front and rear of Tokyo Hy-Power HL-50B 50-watt amplifier

In order to improve the transmitted power limitation, I added to my kit
a Tokyo
Hy-Power HL-50B linear
amplifier. This boosted the five
watts from the FT-817 to fifty watts, which boosted my signal by 10
dB. This was a very worthwhile improvement. There
were two
difficulties with the HL-50B. The first was that it is hard
to
buy, because of the current Part 97 regulations, and so I had to order
it direct from Japan. The second difficulty was that I now
had a
considerably larger kit to tote around, as I could no longer just run
from the internal battery pack on the FT-817. The HL-50B
needed
about 12 amps at 12 volts DC, and that meant that I had to also tote
around either a power supply or a large battery. That having
been
said, it was a great amplifier, and very well built. The
additional 10 dB often made the difference between failure and success
in actually communicating in less than optimal conditions.

I sold my entire FT-817 kit in October of 2004, before my first cancer
operation, to help pay for the hospital bills. While I missed
it,
it would be a couple of years before I would be considering portable
operations again.

Building
the New Go-Kit

During the summer of 2006, I decided to build a new Go-Kit, improved
based on what I had learned from the last one I had. Several
things had changed. First, it was obvious that, post-cancer
treatment, I would not be backpacking equipment anywhere. My
new
Go-Kit would be portable, but meant to be carried about with
assistance, requiring nothing fancier than a little red
wagon. My
new Go-Kit would dispense with the QRP radio with a separate amplifier,
and instead substitute a 100 watt output radio, which could be
throttled back in power as required. The new Go-Kit would
include
an AC power supply, but also be able to run on 12 volts DC.
Additionally, I decided that I would include both a versatile all-band,
all-mode radio, but supplement it with a dedicated 2 meter FM radio,
since it seemed necessary under some circumstances to operate 2 meters
simultaneously with whatever other bands or mode was currently required.

Front view of Yaesu FT-857 Ultra-Conpact Transceiver

The Yaesu FT-857D was chosen as the basis for the new Go-Kit.
It
is extremely compact, operates virtually all modes and almost all bands
from 1.8 MHz to 450 MHz, and outputs 100 watts on HF, 50 watts on 2
meters, and 20 watts on 450 MHz. I have a review of the
FT-857 here.
A Yaesu FT-2800 is the dedicated 2
meter FM radio. It is simple and rugged. I added an LDG
Z-11 Pro antenna tuner, and an Astron
SS-25M power
supply. In order to
have a better view into feedline and antenna conditions, I added a
Daiwa CN-410M power meter/SWR bridge. The 12 volt power is
distributed using a West
Mountain
RigRunner 4005 with five
outputs, using
the standard Anderson Powerpole connectors. Elecronically,
this
setup does exactly what I wanted it to do.

Assembled Go-Kit complete with handles, ready to travel

The Go-Kit is a completely self-contained radio kit, which can be moved
as a unit, and set up with a minimum of fuss and bother. When it is not
in portable use, it lives in a folding desk in our den, and provides a
second operating position. The necessary accessories are
carried
in a separate compartmentalized foam-padded case. A battery,
if
required, is in a separate battery box, which protects its terminals,
and provides a clean case with carrying handles. Using the
Anderson Powerpole connectors, the Go-Kit can also be powered from an
automotive battery or from a car or truck. It is very
versatile.

Go-Kit shown from the operator's position

I built a four-sided enclosure from high grade ¾ inch birch
plywood. The radios are mounted to the enclosure using their
mobile mounting brackets. The power supply was drilled with
extra
holes, and is screwed directly to the plywood base. The
RigRunner
is screwed down also. The other small accessories are
attached
with Velcro tape. The enclosure has a pair of heavy duty
folding
handles installed, one on each end, in order to provide a good hand
hold to pick up and move the box.

Partially-assembled Go-Kit, shown with all of the major electronic
parts mounted

Rear view of Go-Kit showing power distribution and RF routing

The 12-volt power distribution system is based on a West Mountain
RigRunner 4005, which routes the power from the source to all of the
radios and accessories. The source would usually be the 25
amp switching supply shown, but is easily swapped out for whatever 12
volt source is available, whether a gel-cell, automotive power, or a
solar generator. All of the 12-volt power outlets are fused,
which reduces the chance of melting down the insulation on the wiring
harness. It would look neater if it were not for the fact that each
radio has its own unique power plug/jack assembly and fuse, in addition
to the ones supplied in the RigRunner. Once the Anderson
Powerpole connectors are added, it makes it much easier to swap
equipment around, without having to always be looking for the peculiar
molex connector required by each radio, or stripping wires and trying
to hook everything to binding posts like we used to do.

There are a few new lessons learned while assembling and using this go
kit. One is that the tiny new rigs require significant space
around them, both for cooling and also for access to all of their
controls and ports. The FT-857 has controls that extend
around
the front and right side of the removable faceplate, and has a
headphone jack which requires access from the left side. The
Go-Kit must be designed such that all of the controls and ports are
accessible. Another lesson is that mounting brackets must be
spaced to allow the radio mounting screws to be placed between
them. The Yaesu mounting screws have a 7 mm hex head, which
can
be manipulated best with a 7 mm box or end wrench, once they are
started. Starting them required significant patience, and
having
long, skinny fingers would really help also.

12-volt power distribution requires some thought and planning.
Being neat, orderly, and consistent is a great help. Using
the Anderson Powerpole connector system for 12 volt distribution helps
also, but it is not a cure-all. Let's look at some of the
issues:

1. If the 12-volt power you are using does not come from that switching
power supply, then it is necessary to interconnect with some other
source, which may not have the same kind of connectors. I
have a good friend who says that the problem with having standard
connectors is that when you have to hook up to someone else's power,
you have to cut your connectors off to do that. That can be
avoided, if you plan ahead. I have several stubs available
with a Powerpole connector on one end, and stripped leads on the other,
that I can always attach to non-standard sources or equipment.
Go prepared with your own stubs, spare wire, and connectors
to match yours, and this problem can be avoided.

2. Voltage drop becomes a real issue if you need to carry the 12-volt
power very far. For wiring internal to the Go-Kit, I used the
12 AWG wire which came with the FT-857D. According to
the wire table in the ARRL Handbook, it is safe to use 12 AWG
wire with continuous duty currents of 23 amps, and so is safe for this
application. Its resistance is 1.6 milliohms per foot, which
may not seem like much, but which adds up in a hurry. The
cable length back and forth, to supply the FT-857D totals nearly eight
feet (round trip), and simple math shows that the resistance is thus
(1.6 milliohms/foot) X (8 feet) = 0.0128 ohms. At a 20 amp
draw (full power transmit) the voltage drop = (0.0128 ohms) X (20 amps)
= 0.256 volts. So then, on transmit, if the power supply is
supplying 13.8 volts, the amount reaching the radio is (13.80 volts) -
(0.256 volts) = 13.544 volts. That much of a voltage
drop is acceptable. However, let's say that we
choose to power the Go-Kit from a 12.6 volt gel cell battery, and the
battery is 15 feet away, and we use that same 12 AWG wire. For a 15
foot cable, the round trip is twice that or 30 feet. So the
resistance is (1.6 milliohms/foot) X (30 feet) = 0.048 ohms.
The voltage drop on transmit will be (20 amps) X (0.048 ohms)
= 0.96 volts. So the voltage from that 12.6 volt battery
drops to (12.6 volts) - (0.96 volts) = 11.64 volts, which is too low to
operate the FT-857D radio. The answer is to use larger wire,
or shorter cable runs. This has to be considered before you
take your kit into the field.

3. Just because the Anderson Powerpole connectors allow you to hook
anything to anything, does not mean that you can do so without thinking
about the results. It is always necessary to know what you
are connecting, what is a source and what is a load, and which sources
should not be attached to other sources. For the most part, power
supplies and other sources (solar panels, for instance) should not be
hooked in parallel. Doing so is a great way to risk burinig
out one or both power supplies as they fight for control of the
voltage. With some exceptions, batteries should not be hooked
straight across a power supply. It is necessary to think
before acting when working with any power distribution system.
Just because you are working with "merely" 12 volts DC does
not absolve you of the consequences of your actions. In the
heat of an emergency, it is easy to just hook things up and ask
questions later. I urge you not to do that. Stop and consider
what the current flows can be, especially under fault conditions,
before hooking up. And always fuse
those big batteries at the battery terminals, so that if something does
get hooked up wrong, that the fuse blows instead of burning up big
wires and starting fires.

Conclusions

This Go-Kit works as I intended it to. The plywood was from
scrap
shelving, and so it cost very little to build, apart from the cost of
the electronics. It is very sturdy, and provides significant
mechanical protection for the electronics. Because it is used
in
daily operation, I have confidence that it will work when the next
community service event occurs. All-in-all, I am pleased with
the
project.

73

Diehl Martin
W4TI
August 2006

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